Hmm ..... not looking good ....
You could take things back a stage further:
The 25VAC comes directly off the transformer, but it does pass through fuses F3&F4 before it hits the molex, so might be worth taking a reading before the current passes through those fuses.
The 10.6VDC comes off the rectifier (or arrangement of four diodes if you prefer) so again, you may want to check what AC voltage the transformer is supplying into the rectifier.
That said, the 6.5VAC comes straight off the transformer and into the molex (there is a fuse for that, but it's usually buried on the floor of the cab, close to the on/off switch so you can rule that out) so it looks like the transformer isn't doing it's job.
Which leads me to conclude that you've got a duff transformer. It's odd, as the transformer is clearly giving you the 125VAC that you need to run the monitor, so I'd say one/two/more of the windings inside the transformer have blown - which is highly unusual.
I say unusual .... but the transformer side of the assembly is protected by fuses F1&F2, and someone has bypassed F2 which might explain it.
Solution ...... I guess you could in theory replace the transformer - but it needs to output the same set of voltages as the one you do have should output, and I doubt it would be an easy job anyway. I reckon you need a replacement power assembly. I can post a partial list of suitable donor cabs later.